2 Brush DC generator regulator circuit help

Thread Starter

Dwayne Rothe

Joined May 26, 2016
12
Hi all, I have a 1949 Velocette LE motorcycle which uses a 6v DC POSITIVE GROUND electrical system. It has a 2 brush P. E.C DC generator putting out approx. 30 watt/5A charge(8-14v unregulated), as stated this is a positive ground system currently using the original shunt/cut-out type mechanical regulator which is past it's use by and impossible to find a replacement for. I can find somewhat expensive electronic replacements but would like to build my own. Any help on a suggested circuit would be really appreciated. :)
P. S attached pic is of the distributor/charge system, where you can see the old cut-out reg.
 

Attachments

shortbus

Joined Sep 30, 2009
7,857
Is there a reason you want to keep the positive ground? That said on another forum ETO there is a thread where a member was making a regulator for an old 6V Volkswagen. He, with the help of the other members came up with an electronic solution that would fit in the original VW regulator case, so you might want to go there and look at what he did and why he did what it took to work. If I remember right his forum name is VWdan or something similar
 

schmitt trigger

Joined Jul 12, 2010
312
Even if you would like to keep the positive ground, with semiconductors you always have the option of complimentary devices.

If I remember correctly, in motorcycles the dynamo simply cuts out the field voltage when an over voltage is detected, and re applies it when the voltage drops
 

MaxHeadRoom

Joined Jul 18, 2013
21,274
If it use wound field control via a field interruption type contacts, you could possibly use a electronic version using a LM311 etc, this method was used to replace the mechanical interrupter type regulator in the old battery charging systems.
Max.
 

Thread Starter

Dwayne Rothe

Joined May 26, 2016
12
Is there a reason you want to keep the positive ground? That said on another forum ETO there is a thread where a member was making a regulator for an old 6V Volkswagen. He, with the help of the other members came up with an electronic solution that would fit in the original VW regulator case, so you might want to go there and look at what he did and why he did what it took to work. If I remember right his forum name is VWdan or something similar
Apart from not wanting to re-wire the electrics I would like to keep the bike as close to original as possible, it's not a daily rider so the 6 volt system is suffice for now, with that said I once was considering a retro fit electronic ignition/charge system and switching to 12V Neg. ground!
 

Thread Starter

Dwayne Rothe

Joined May 26, 2016
12
Even if you would like to keep the positive ground, with semiconductors you always have the option of complimentary devices.

If I remember correctly, in motorcycles the dynamo simply cuts out the field voltage when an over voltage is detected, and re applies it when the voltage drops
YES that's correct, it use an electromagnetic core which opens and closes a set of contact points to apply/break the charge circuit which works but has it obvious weakness in the points wearing.
 

Thread Starter

Dwayne Rothe

Joined May 26, 2016
12
If it use wound field control via a field interruption type contacts, you could possibly use a electronic version using a LM311 etc, this method was used to replace the mechanical interrupter type regulator in the old battery charging systems.
Max.
Hmmm using an Op-Amp comparator circuit?

 

shortbus

Joined Sep 30, 2009
7,857
Apart from not wanting to re-wire the electrics I would like to keep the bike as close to original as possible,
Other than switching the battery leads and re-flashing the generator I don't know what other rewiring would be needed. I'm not familiar with your make of bike, but I did the positive to negative ground thing on my 1957 Harley before I changed over to 12V.
 

Thread Starter

Dwayne Rothe

Joined May 26, 2016
12
Other than switching the battery leads and re-flashing the generator I don't know what other rewiring would be needed. I'm not familiar with your make of bike, but I did the positive to negative ground thing on my 1957 Harley before I changed over to 12V.
My only problem would be the charging system, the generator is built into the engines housing and only puts out 30W@6V so wouldn't successfully supply enough charge
 

shortbus

Joined Sep 30, 2009
7,857
My only problem would be the charging system, the generator is built into the engines housing and only puts out 30W@6V so wouldn't successfully supply enough charge
No, I didn't mean to change to 12V. Keep it 6V but just change the ground to negative. Then you coulld keep it looking like original and use a easier to find regulator. You when changing ground polarity would need to "flash" the generator to establish the new polarity, just like putting a new generator on the motor.
 

Thread Starter

Dwayne Rothe

Joined May 26, 2016
12
No, I didn't mean to change to 12V. Keep it 6V but just change the ground to negative. Then you could keep it looking like original and use a easier to find regulator. You when changing ground polarity would need to "flash" the generator to establish the new polarity, just like putting a new generator on the motor.
Sorry I misread that. Well yes as you pointed out,it is not that difficult to achieve just might be the easiest solution. Thanks :)
 
Top